Air flow control for pneumatic classifying system



AIR FLOW CONTROL FOR PNEUMATIC GLASSIFYING SYSTEM Filed on. 5. 1961 K GRANULAR I I MATERIAL FIG.4

INVENTOR. JEAN-PAUL VANDENHOECK ATTORNEYS United States Patent 3,180,492 AIR FLOW CONTROL FOR PNEUMATIC CLASSIFYING SYSTEM Jean-Paul Vandenhoeelr, New York, N.Y., assiguor to Buell Engineering Company, Inc., New York, N.Y., a corporation of New York Filed Oct. 5, 1961, Ser. No. 143,224 3 Claims. (Cl. 299-433) This invention relates to the classification and collection of granular material, and, more particularly, to the classification and collection of granular material utilizing a flowing gas to withdraw relatively fine partcles of the material.

In industries in which a granular material forms a working product, it is oftentimes necessary to classify the material into various groupings of particularly sized particles. To ensure that any individual grouping contains particles only of a certain size, e.g., of a size greater than that of a predetermined reference particle, it is necessary that the classification process employed be adapted for fine control. Further, if a number of individual classifying units are to be utilized, each of which contributes to the same grouping of particles, it is necessary that the classification throughout the units be uniform.

The present invention is directed toward uniformly classifying and collecting granulur material, using any number of classifying units that are adapted to classify the material by employing a flow of' gas therethrough. A resistance member is provided for each unit through which the gas, coming from a common source, must flow. The resistance to the flow of gas provided by each member is large with respect to the resistance to the flow within the classifying unit itself. Thus, the flow of gas through each of the units is determined by the associated resistance member alone. Since this flow determines the classification, and since the resistance members arechosen to provide equal flow resistances, a uniform classification throughout the units results, regardless of the distribu tion of the granular material.

The invention further contemplates a unique cut-01f device positioned in the discharge pipes of all the classifying units to prevent an equalizing flow of gas to the units through a common outlet conduit. Such an equalizing flow would destroy the effects of the resistance members.

Although the invention has been described above in general terms, a better understanding of it may be obtained by consulting the following detailed description, which is to be read in conjunction with the appended drawing, in which:

FIG. 1 is a fragmentary view in perspective showing a pair of classifying units embodying the principles of the present invention;

FIG. 2 is a diagrammatic view of a classifying system employing the units shown in FIG. 1;

FIG. 3 is a fragmentary sectionai view of a portion if the apparatus shown in FIG. 1 taken along the section line 3-3 of that figure and looking in the direction of the arrows, showing the details of a gate mechanism that regulates the flow of granular material to a classifying unit; and

FIG. 4 is a fragmentary sectional view of a portion of the apparatus shown in FIG. 1 taken along the section line 44 of that figure and looking in the direction of the arrows, showing the details of a gas seal flap.

Referring to FIG. 1, a granular material from a source (not shown) is applied to an input pipe 11. The material flows through the :pipe 11 and into a series of input lines 12a, 12b only two of which are shown in the figure, that are coupled to input sections 14a and 3,130,492 Patented Apr. 27, 1965 ice 14b of similarly constructed classifying units 15a and 15b, respectively.

Referring by way of example to the unit 15a, the granular material flowing into the input section 14a passes through an adjustable gate 16a. As shown in FIG. 3, the gate 16a is capable of being maintained in a plurality of positions intermediate the open and closed positions shown in dotted and full lines, respectively. During classification the gate 16a is retained at least partially open, and the granular material, as shown at 17 in the input section 14a, passes through the gate to form a thin curtain of material flowing in front of a plurality of bafile plates 19a. At all times during classification there should be enough granular material in the section 14a to ensure that a gas seal is formed in the gate 16a.

Referring again to FIG. 1, a flowing gas from a gas conduit 21 is introduced into the classifiers 15a and 15b through a pair of perforated resistance plates 20a and 20b, respectively, as shown by the arrows. Again using the classifier 15a as an example, the gas flowing through the perforated resistance plate 20a sweeps through the curtain of granular material formed in front of the bafiie plates 19a and carries fine particles of the material through the plates to the apparatus shown in FIG. 2.

The perforated resistance plates 20a and 20!; shown in detail in FIG. 1 are constructed to provide gas flow resistances that are large with respect to the gas flow resistances provided by the granular material within the classifying units. Accordingly, the flow of gas through each unit is dependent almost entirely upon the flow resistance of the associated perforated resistance plate. It is this flow that determines the degree of classification within a unit. Thus, since the classifying units have equal cross-sectional dimensions and since the perforated plates are constructed to provide equal flow resistances, the rates of gas flow through the classifying units are equal, thereby providing classifications throughout the units that are uniform and not dependent upon the distribution of granular material.

The granular material Within the classifying units 15a and 15b of FIG. 1, not swept through the baillle plates 1% and 19b, passes downwardly through a series of horizontally positioned bathe plates 22a and 2211, respectively, provided in the units to eliminate turbulences. Referring again to the classifier 15a as an example, the granular material passing through the bafile plates 22a impinges upon a plate 24a and passes therefrom into a discharge member 25a.

Referring to FIG. 4, the discharge member 25a leads into a common outlet conduit 26 through a flexible flap 27a. When no granular material flows through the dis charge member, the flap 27a is in the positionshown in full lines, thereby closing off the discharge member from the outlet conduit 26. When granular material passes through the discharge member 25a, however, the flap 27a is forced to the open position shown in dotted lines, and granular material passes into the outlet conduit. In this fashion the flap 27a and the flap 27b (not shown) prevent the classifying units 15a and 15b from being coupled together through the common outlet conduit 26 when no granular material is passing through either one of the associated discharge members. Such a coupling between units would equalize pressures throughout the units and destroy the efiects of the perforated resistance plates 20a and 20b. For this same reason, i.e., to prevent the equalization of pressures throughout the units, the granular material is kept at a level in the input sections 14a and 14b sufiicientlc high to ensure that no gas leaks through the gates 16a and 16?).

FIG. 2 shows a system for classifying and collecting granular material. The system comprises classifying units 15a through 152, which include associated perforated resistance plates 20a through 20s, respectively. The system is not limited, of course, to the number of units shown. Each of the units 15a through 156 operates as described above, and gas entrained fine particles of granular material pass through the baffle plates 1% through 1% and are discharged into a chamber 2h. Most of the fine particles of granular material drop downwardly and are passed out of the'chamber 29 through an outlet 30. The gas, with the remaining portion of the fine particles of granular material, is drawn by a fan arrangement 31 into another chamber 32 out of which the remainder of the fine particles fall through an outlet 34. The gas, drawn by the fan 31, passes upwardly through a conduit 35 and through the fan into the gas conduit 21 'to'be reapplied to the classifying units 15a through 15c.

Coarse particles of granular material, not passing through the bafiie plates 19a through 19d, pass via the discharge members 2511 through 25d into the outlet conduit26 (shown only in FIGURE 1), which lead into a coarse material outlet 36. Coarse particles 'from the classifying unit 15e drop directly into the coarse material outlet. 7

A unique arrangement'for providing a uniform classification of granular material throughout a plurality of classifying units has been described; This arrangement is, of course, subject (to modifications which will depart from the exact form of the apparatus shown, but which 7 will, nonetheless, be truly embraced within the inventive concepts involved. For this reason, such modifications should be deemed to be encompassed by the following claims which are set forth to define the invention.

7 What is claimed is:

1. A classifying and collecting system for granular material, comprising means for applying a granular material to a plurality of classifying units each of which utilizes a separate flow of; gas therethrough to classify the granular material, each of the classifying units having a gas input with a perforated plate positioned therein through which gas must flow to enter the classifying unit, the perforated plates all having substantially equal resistances to the flow of gas thereithrougn'each of said resistances being large with respect to the gas fiow resistance provided by the granular material within each of the classifying units to provide a fiow of gas through 7 'each' unit dependent almost entirely upon the flow resistance of the perforated plate inthe input of said unit,

a gas outlet coupled to each of the classifying units, a conduit member coupled to all of the gas inputs, means for applying a flowing ,gasto the conduit member to provide for the passage of substantimly equal portions of the flowing gas through the perforated plates and into the classifying units to carry away fine particles of the granular material through the gas outlet, means for collecting the fine particles of the granular material carried by the gas through the gas "outlet, and means for collecting from each of the classifying units coarse particles of the granularimaterial not carried away by the gas flowing through the classifying units.

2. Apparatu as recited in claim 1 wherein the means for collecting the coarse particles of granular material comprises a common outlet conduit, a plurality of discharge pipes each of which couples a different classifying unit to the outlet conduit for conveying the-coarse particles of granular material from the units to the conduit, and means for closing off each discharge pipe when no granular material is flowing therethrough, thereby preventing a flow of gas from one classifying unit to another.

3. Apparatus as recited in claim 2, wherein the closing off means comprises a plurality of flexible flaps each of which is positioned across adifferent discharge pipe and each of which is biased in a position to close off its associated pipe, the positioning of each flap being such that a flow of granular material through the associated dis charge pipe urges the flap away from its biased, position, thereby opening the discharge, pipe into the common outlet conduit and allowing the granular material to flow into the conduit.

. References Citeii by the Examiner" V UNITED STATES PATENTS HARRY B. THORNTON, Primary Examiner.

ROBERT A. OLEARY, HERBERT LT MARTIN,

r Examiners. 

1. A CLASSIFYING AND COLLECTING SYSTEM FOR GRANULAR MATERIAL, COMPRISING MEANS FOR APPLYING A GRANULAR MATERIAL TO A PLURALITY OF CLASSIFYING UNITS EACH OF WHICH UTILIZES A SEPARATE FLOW OF GAS THERETHROUGH TO CLASSIFY THE GRANULAR MATERIAL, EACH OF THE CLASSIFYING UNITS HAVING A GAS INPUT WITH A PERFORATED PLATE POSITIONED THEREIN THROUGH WHICH GAS MUST FLOW TO ENTER THE CLASSIFYING UNIT, THE PERFORATED PLATES ALL HAVING SUBSTANTIALLY EQUAL RESISTANCES TO THE FLOW OF GAS THERETHROUGH, EACH OF SAID RESISTANCES BEING LARGE WITH RESPECT TO THE GAS FLOW RESISTANCE PROVIDED BY THE GRANNULAR MATERIAL WITHIN EACH OF THE CLASSIFYING UNITS TO PROVIDE A FLOW OF GAS THROUGH EACH UNIT DEPENDENT ALMOST ENTIRELY UPON THE FLOW RESISTANCE OF THE PERFORATED PLATE IN THE INPUT OF SAID UNIT, A GAS OUTLET COUPLED TO EACH OF THE CLASSIFYING UNITS, A CONDUIT MEMBER COUPLED TO ALL OF THE GAS INPUTS, MEANS FOR APPLYING A FLOWING GAS TO THE CONDUIT MEMBER TO PROVIDE FOR THE PASSAGE OF SUBSTANTIALLY EQUAL PORTIONS OF THE FLOWING GAS THROUGH THE PERFORATED PLATES AND INTO THE CLASSIFYING UNITS TO CARRY AWAY FINE PARTICLES OF THE GRANNULAR MATERIAL THROUGH THE GAS OUTLET, MEANS FOR COLLECTING THE FINE PARTICLES OF THE GRANNULAR MATERIAL CARRIED BY THE GAS THROUGH THE GAS OUTLET, AND MEANS FOR COLLECTING FROM EACH OF THE CLASSIFYING UNITS COARSE PARTICLES OF THE GRANNULAR MATERIAL NOT CARRIED AWAY BY THE GAS FLOWING THROUGH THE CLASSIFYING UNITS. 